Go to Quanzhou, Fujian Province to debug three 15KW frequency converters for textile machines. The reason is that the inverter always triggers the hardware protection "OCU 1". After I arrived at the scene, I made a static test on the machine, and the main circuit and control circuit were in good condition. I used a multimeter to measure that the zero line and the ground line are connected together, and I didn't know that the zero line in their factory was used until I asked an electrician. In general, when the inverter is grounded, if the factory's zero line and ground wire are used as * * *, it is best to connect the ground wire from another place and remove the ground wire to solve the fault.
Fault analysis: Because the factory's zero line and ground wire are used for * * *, and the inverter ground wire is also connected to the zero line, it will generally spread interference signals. Our inverter reports "OCU 1" failure under the following conditions: 1. There is a short circuit on the three-phase output side of the frequency converter; 2。 The inverter module is damaged; 3。 External interference signals enter the frequency converter.
Because the first and second reasons are normally excluded, only the third external interference signal enters from the ground wire, so removing the ground wire will cut off the interference source. At this point, the inverter resumed normal operation.
Second,
Debugging of induced draft fan for 55KW boiler in Fuqing City. The fault is also "OCU 1". Usually our "OCU 1" faults are: external interference, short circuit of three-phase output, and internal fault of the machine. The reason is that the machine will be reported as soon as it runs to 10HZ. (The inverter is used for free parking, and the inertia of the fan is relatively large. The user should always start and stop the frequency converter. This shows that there are not too many machine problems, but interference problems. (Because the motor line is tens of meters long, the control line and the main power line are mixed together) After stopping the frequency converter for half an hour, observe that the induced draft fan is still rotating. I changed the inverter parameters to "brake first, then start" (F0-0 1 1= 1). Of course, there are some parameters to be changed, so I won't explain them here. You can download the technical manual from our website. ) start the inverter again, and the fault has not been ruled out. After using several schemes, we finally increased the starting frequency to 3HZ(F0-0 12=3), and the problem was solved. What's the problem
Third,
Frequency conversion transformation of a 18 double-frame copper-clad plate vacuum hot pressing unit on Jiangmen wood-based panel machinery, the tubing vibration is large, the noise is large, and it runs normally at the working frequency.
The unit consists of two vacuum inclined shaft pumps, a charging pump and a booster pump (these are four reformed machines). A loading and unloading frame, a mobile loader and corresponding hydraulic system, vacuum system and electrical control system. A * * * uses three 55KW and one 75KW frequency converters, all of which run at multiple speeds.
After arriving at the scene, it was found that it was the noise from the pipes of two inclined shaft pumps. Raising the lower limit frequency to 30HZ (the original 20HZ) is still not feasible. Several schemes have been used, but the problem still cannot be solved. By observing that this noise was generated when the inclined shaft pump was accelerating, it was later thought that the multi-speed acceleration and deceleration time was set too long, and the deceleration time was adjusted to 5HZ (originally 15HZ, the vacuum pump load was generally not very heavy), and the noise disappeared.
Four,
I've encountered a thorny problem. Here's the thing. A customer called me and said that a number of machines in our company are controlled by the upper computer. If you give the start instruction, you can start it, but if you give the stop instruction, you can't stop it. As described below,
40 1 1-22KW fans were reformed for energy saving, and each inverter was controlled by an upper computer DDC module (made in Canada). The upper computer mainly monitors the fault alarm, filter alarm, frequency, start-stop and temperature of the inverter. Everything is normal except that there is trouble when starting and stopping. Later, I came to the scene to detect the fault, and then I looked at the instructions of the DDC module of the upper computer. Finally, I found that the dry contact of DDC module does not accept DC 24V, but only accepts AC 24V or passive signals, so this phenomenon appeared. Later, it was solved by adding a relay.
Five,
It is also a frequency converter controlled online with the upper computer. The fault is that the upper computer gives the running signal, but the frequency converter does not receive it. Everything else is normal, the inverter itself can run, but it can't be connected to the upper computer. I told the customer to check the line again, but the user insisted that it was nothing, no problem. I thought it was a faulty line. Later, when we went to the scene to deal with it, we found that a 24V cable was not connected properly.
Go on, let's talk about some interference problems:
1. When users report that PLC sends signals to the frequency converter, unnecessary faults often occur, such as giving an error message or the frequency converter not receiving the information. Because the customer was in urgent need, we rushed to the scene to deal with it, and detected that the frequency converter, PLC, power supply and equipment were all normal. It is preliminarily determined that it is caused by interference. We connected the filter to the power module and input/output power cord of PLC, but the problem still hasn't been improved obviously. Later, the inverter was put into use. ..
2. Recently, customers reported that the speed control system composed of three inverters (installed in the same inverter cabinet) has the following conditions: when using an external potentiometer to adjust the frequency, it is found that the speed fluctuates, and then an error will be reported. After arriving at the site, check that the power supply, load, potentiometer and control circuit are all normal. When debugging frequency converters, one frequency converter works normally when it runs alone, while three frequency converters will be abnormal when they run at the same time.
Countermeasures: Move the three inverters out of the inverter cabinet, put them into a separate inverter cabinet, separate the potentiometers, and then switch to shielded wires. Finally, the interference is removed, and the three can run at the same time.
A few days ago, I received a phone call from a user, saying that a printing machine should be reformed to save energy and run in multiple files. (3。 7KW) It is normal for the inverter to run the printing press alone. When it runs synchronously with the paper feeder of the printing machine, it reports the software overcurrent fault. The agent technician adjusted it for a day, but it was confirmed that our machine was faulty and could not be used, so we had to return it.
Later, I went to the site for maintenance and treatment, circuit testing, and the inverter was fine. Look at the equipment, there are two motors in the printing machine, one is the main motor, (that is, the modified 3. 7KW), and one is for the paper feeding device, which plays a lifting role. When the frequency converter runs alone, the printing machine is normal, that is, when it runs synchronously with the paper feeder, the printing machine fails. These actions are accomplished by contactors and relays. The printing machine equipment is not grounded, and the grounding of our inverter is connected to the printing machine equipment, so there is no grounding at all, which is considered as an interference fault.
Countermeasures: a, replace all control lines with shielded lines and add magnetic rings;
B, adding a magnetic ring on the power cord;
C, grounding the equipment and the frequency converter respectively, and finally troubleshooting.
Go on, talk about the line fault encountered at the scene.
1。 When I was on a business trip in Fujian Province to do after-sales service, our agent's customer had a Leng Ci 5.5KW inverter that kept tripping. The machine was sent out for repair twice, but it didn't work well when it was brought back. The maintenance staff didn't see anything wrong so far, but I happened to meet a customer who told me about it and wanted to see it on the grounds that I was interested. So far, I have seen the scene. This machine is connected with a frequency converter controlled by an upper computer. Many control lines; The ambient temperature at the scene is also very high, and you will sweat after standing for a while; This machine has been used for several years. Based on these points, I suspect that the line is short-circuited. I removed all the control lines without load; No-load operation is normal for half an hour, and it is normal after loading. When the control line is connected, it will report a fault. This makes my heart a little low. I removed all the control lines and measured them. Finally, it is found that two lines are aging and short-circuited, and other lines are aging to varying degrees, but not so serious. Replace all control lines, run the frequency converter, and everything is normal.
2。 The air compressor adopts 1 10KW frequency converter of a textile factory in Zhejiang, and adopts PID control. It didn't show up when it was powered on recently, and there was no 24V. Everything else is normal. The agent's technicians went to the scene to replace the circuit board, but it still didn't work. When the frequency converter is reformed, the bypass remains unchanged. The customer was very anxious and called the company several times. After arriving at the site, check whether the frequency converter is normal. After removing the control line, run the frequency converter alone in good condition. But the 24V circuit is burnt out, and it must be caused by a short circuit. The user's control line is not routed against the wall, but from the ground, which is also random and messy. This is a low-level mistake. The measurement of the control line shows that there are many damages and short circuits, all of which are crushed by hard objects.
3。 Last month, I went to a coal mine enterprise in Jiangxi to deal with a 160KW domestic frequency converter. The fault reason is that overload protection is always skipped, so there is no problem in no-load operation and the three phases are balanced. Because this machine has passed the warranty period, the customer is afraid of returning to the factory. I happened to be on a business trip in Jiangxi, and I was entrusted by my client to come and have a look. The scene environment really dare not think! I still have shadows. It takes at most 10 minutes to enter the site, and only half an hour to wear a mask. There is too much coal ash, which smells bad. I'm sorry. Let's talk about my feelings again and get to the point.
I checked the external wiring at the scene, the operation console is normal, the inverter three-phase is normal, and there is no problem with the current detection circuit on the circuit board. What's the problem? I thought the resistances of Hall sensor, Hall wire and measuring sensor were all normal, maybe the Hall wire was broken. I took it down and measured it with a multimeter, and found that there was really a broken signal line, so it was normal to run the inverter after welding with an electric soldering iron.
This frequency converter is installed next to the motor, which may be caused by vibration! Of course, there are many reasons. This is just my personal opinion. Of course, it is unreasonable for the inverter to be installed next to the motor. I hope everyone will pay attention.
4。 I have used four 18.5 frequency converters on a piece of equipment, and all of them have undergone strict debugging before leaving the factory. But when I arrived at the user's site, the electrician told me that the other party always tripped when it was idle, sometimes one inverter tripped when it started, and sometimes two inverters tripped when it started.
I checked it after I arrived at the scene, and all the wiring, frequency conversion parameter settings and hardware were useless. When I went to the factory's total vacant room, I found that their vacant room was temporarily borrowed. The ground wire and neutral wire were short-circuited and had leakage protection function, only 30mA. The Technical Manual states that the leakage current of each inverter should not exceed 30mA. Remove the leakage protection wire and the fault will be gone.
According to these field experiences, it is suggested that our users should consider whether the wiring and installation meet the safety specifications when installing the inverter. If possible, it is best to install PV tubes or copper-aluminum-iron tubes, which can protect and shield the lines. If possible, it is recommended to install a bypass, which will avoid a lot of trouble.
Some noticeable problems in the near future. For everyone to share.
1. In June this year, we received a phone call from a customer, saying that our 15KW inverter was seriously heated when it was loaded (this machine has been used for more than a year) and wanted to go back to the company for maintenance. I asked him if the motor was hot, but he said he didn't notice. After the inspection, he called and said that the motor was also hot. I asked him to replace the frequency converter with another motor to see if there was such a phenomenon. Later, it was said that it was not normal, but 18.5KW was still brought. Finally, the user knew what to do without me, indicating that there was something wrong with the motor. So when we encounter problems, don't worry, calm down and slowly check the reasons. All failures have cause and effect, don't they?
2. An inverter of 1 10KW was built today. The fault was caused by the explosion of inverter and electrolytic capacitor caused by high temperature. It's summer now, and the high temperature continues to rise in many places. We should pay more attention to it! If your inverter is used in a place where the temperature is too high, improving the environment is the best policy.
I received a letter for help from my colleague today.
The details are as follows: He installed a 18.5KW boiler induced draft fan for customers. 5KW frequency converter, once installed and started, the transformer room will jump as soon as it is opened. The original distribution room is equipped with leakage protector (action 200mA, pulse 30mA). The customer's request to remove the leakage protection was rejected, and then the carrier frequency was adjusted to 1KHz. Changing the startup mode of the inverter still failed to solve the problem. Finally, it is suspected that the power cord of the motor is leaking, because it is about 20 meters long and buried underground, but it is difficult to ask customers to replace it (its original power frequency is normal). Is there any simple and effective solution? Thank you for your help!
Answer; Generally, the leakage protector will trip when it detects that the three-phase imbalance is above %20. When the frequency converter is installed, the three-phase imbalance will generally exceed %50, so the leakage protector will definitely trip. Below I give several methods, hoping to help you.
Method 1: there is generally a regulator on the leakage protector, just raise it;
Method 2: Replace the special leakage protector for frequency converter, which is available in the market.
Method 3: increase the equipment load, that is, the motor load, and the starting leakage current will not be very large.
Method 4: Short-circuit leakage protector.
5. I recently encountered a debugging problem of on-site inverter, which is worth learning, so I sent it to share with you!
The specific problems are as follows: A customer in Shandong called to report that a 75KW inverter always skipped the "OC" protection fault in operation. According to experience, this fault is difficult to handle, because there are several cases of "OC" fault: 1. There is a short circuit on the load output side of the machine; 2。 The load is too heavy and the acceleration time is too short; 3。 The inverter module is damaged; 4。 External interference signals, etc.
The user indicated that these phenomena have been considered. It doesn't matter whether the power frequency of the load is used. The acceleration time has been set to 60S, and the inverter is equipped with a reactor. The most important point is that the inverter runs normally with no load. Hearing this, I was depressed for a long time. Finally, I asked the user whether the inverter had been repaired or whether it had been operated. After a while, the user called me back and said that the main control board of this inverter had been replaced by an electrician. Because the display of this 75KW inverter was abnormal, the electrician removed it from a spare 37KW inverter machine and replaced it with a new one. Because the main control boards of our company's 37KW and 75KW inverters are the same, but the parameter settings are different, so the electrician will confidently replace them. The parameters of 37KW inverter are consistent with those of 37KW motor, but definitely different from those of 75KW motor (such as current, power, number of poles, revolutions, current sampling, etc.). ). So if it is used on 75KW, it will definitely report "OC" failure. Users are advised not to repair the inverter easily without knowing the situation. If they don't know much about frequency converters, they can find technicians in this field first, or they can directly find manufacturers.
6. I received a complaint call from an agent customer, which reflected that four MM440 inverters were used on one device. The agent tried all the parameters of the inverter at home, and the inverter worked normally. However, when electricians connect inverters at the user's site, the AC power supply is always disconnected. Sometimes one inverter trips when it is started, and sometimes two inverters trip when it is started.
I checked it after I arrived at the scene, and all the wiring, frequency conversion parameter settings and hardware were useless. When I went to the factory's total vacant room, I found that their vacant room was temporarily borrowed. The ground wire and neutral wire were short-circuited and had leakage protection function, only 30mA. The MM440 user manual indicates that the leakage current of each inverter will not exceed 30mA (because the leakage current can reach more than 50MA after switching to the inverter). Just remove the leakage protection wire.
Seven. Recently, I went to Hebei to debug a number of frequency converters, mainly used in rubber mixers and rubber used in cables. I didn't know it was used in a rubber mixer at first, but the customer said it was used in fans and pumps. Therefore, the frequency converter is fan-pump type. I saw it as soon as I arrived! This is the load of the fan and water pump. Isn't this a bluff? ! The customer's technicians also said that this is a light load and also requires closed-loop control. I said, is there feedback, pressure and flow? He said no, it needs closed-loop energy saving anyway. This makes me dizzy. Later, under the arrangement of the leader, I installed one and tried it, but it could not be started at all. Over-current protection was ensured as soon as it was put into operation, and the overload rate reached 180%. This kind of site is not suitable for frequency conversion transformation. Later, customers asked for transformation, so they had to replace all heavy-duty frequency converters to solve the problem! It is really grinding! !
Eight. Recently encountered a more troublesome problem? It is now published for everyone to share. The specific questions are as follows:
I received a technical support call from an agent yesterday, which reflected one of our three models. The 4KW clock knitting machine uses 7KW frequency converter. After running for several hours, the motor stopped running. However, the frequency converter also has a frequency display and does not report a fault, that is, the motor does not turn. I thought there was something wrong with the inverter, so I replaced it with a new one. The fault remains the same.
In the past, the' XX' inverter was damaged, and now it is a difficult problem to refit our inverter. Later, it was found that when the forward button was pressed, the forward and reverse indicator lights up when the inverter was running; That's weird. Is it caused by interference again? After we switched to shielded wire, everything was fine.
Nine. Recently, I received a phone call from a user engaged in mechanical equipment, which reflected that our inverter interfered with the touch screen on his mechanical equipment. The specific faults are as follows:
The user said that the touch screen of the device often turns blue when used. If you can't see the data, the fault will disappear as long as you power off and power on again. After more than ten minutes, the fault began to appear again, and the user requested technical support for on-site treatment.
Fault analysis and treatment: after we arrived at the scene, we found that the frequency converter was controlled by the touch screen, and checked that the frequency converter, external control circuit and equipment were all normal. Try a new inverter for a while, and the fault still exists. After replacing the control line with shielded wire and magnetic ring, the fault is still unresolved.
Finally, I suspect there is something wrong with the touch screen. I unplugged the power cord of the touch screen and plugged it back in, and the fault disappeared. After a while, the fault appeared again, and the signal line plugs were all unplugged, but there was still a problem.
That's weird. Where is the interference? Then I suddenly thought of the grounding wire behind the touch screen and took it off. The equipment operated normally for an hour without any trouble. Later, it was detected that the grounding was poor and the grounding resistance was large.
With Tenuto last year (2007) 65438+February, I went to a construction site in Xijiang to deal with an interesting fault. I believe this problem is helpful to everyone.
This user has used our company's 160KW frequency converter, and the operation panel adopts remote monitoring, and the wiring length reaches 150M.
Fault phenomenon: When the inverter is started, the display on the operation panel is fuzzy and the numbers are constantly jumping. After running to the normal frequency, it sometimes jumps and sometimes flashes. It seriously affects the operation and use of users, and needs our technicians to deal with it on the spot.
Treatment and analysis: After arriving at the site, I saw the whole operation process, and it really kept flashing as the customer said. According to experience, this kind of fault must be online. Because of the long wiring and loss, the machine was installed by the agent, and the 150M remote line was also made by the agent himself. Check whether the panel wire is shielded and whether the other end is shielded and grounded. According to the standard, this application belongs to normal connection, but I have used several methods, such as adding magnetic rings and rewiring. Finally, I adopted the method of shielding grounding at both ends, which has obvious effect and completely relieved the flashover fault.
I don't know if the friends here have ever encountered such a failure. Welcome to share!
An industrial control friend asked me this question, as shown below.
What's the difference between zero line and ground line?
1. Zero line and ground line are two different concepts, not the same thing.
2. The grounding potential of the grounding wire is zero. The nearest point of the electrical appliance used is grounded.
3. The ground potential of the neutral line is not necessarily zero. The nearest grounding point of the neutral line is at the substation or power supply transformer.
4. The zero line is sometimes shocking. What time? When your electric stove is not hot, don't think it is dead and won't shock people. That's wrong!
5. The ground wire won't electrocute people, unless the situation is bad, the designer doesn't understand it, or the product is made casually!
6. If there is a neutral wire and a ground wire in your circuit, you will find a high withstand voltage capacitor between them.
12. Some altar friends reported the "OCU" fault problem of the inverter, and now we propose some treatment methods as follows:
The Chinese meaning of this fault is: "Software overvoltage" probably means overvoltage fault, which is probably the most common fault in frequency converters.
1. First of all, troubleshooting caused by parameter problems (such as current limiting parameters and short acceleration time may lead to overcurrent);
2. Then we can judge whether there is a problem with the current detection circuit (such as Hall sensor and Hall line fault). Whether the output side of frequency converter is short-circuited).
3. Whether the grid voltage is too high;
4. There is interference signal outside.
Thirteen, a few days ago, an industrial control friend from Jiangxi wrote to me. The contents of this letter are as follows:
Hello, Teacher Fan, I have a frequency conversion water supply equipment, which adopts closed-loop control and 30 KWABACS 4 10 frequency converter. After more than one year's operation, there is such a situation: the motor does not turn, but the inverter displays the output frequency of 4.2 or 4.3HZ, and the inverter does not report the fault. At this time, there is no water in the external pipe network, and it will start normally after power failure. The same is true after running for four or five hours. The actual motor is about 50 degrees. I have blocked this function or reported it. Please take the time to help me analyze the possible reasons, thank you!
Solution:
Later, the "overheating" fault was reported in the debugging. Based on these, I give the following opinions:
1。 This should have little to do with the motor. It is normal for the temperature of the extension to be 50 degrees. You can run it to see if the current and voltage change greatly, and check the motor with a shaking table. If it is normal, it means that the motor is not a big problem.
2. Because the closed-loop control of the inverter shows 4.2HZ, the sensor feedback is a bit wrong and normal.
3. Check whether the variable frequency fan works normally, or one fan does not rotate, or rotates slowly due to aging. Open the rear panel to see if the air duct is not smooth, such as too much dust and debris.
4. If not, it means that there is something wrong with the frequency converter, for example, the temperature detection switch is damaged and the temperature detection circuit is faulty.
Finally, my friend told me that the problem was solved. He said: "There was a lot of dust when the inverter was turned on. After cleaning, add a fan for forced ventilation. It has been running normally for almost two days now. "
Let's call it a day. Of course, there are many more. Save them for the next upload! Some fault codes in this paper were analyzed by Zhong in our company's product technical manual. If you want to know more, or want to know the technical manual, you can leave me a message and welcome your valuable suggestions.
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